Systemic analysis of transcriptome in cancer and precancerous lesion of the esophagus and stomach

为了了解食道癌和胃癌发生发展的详细分子机制，我们通过基因表达序列分析(SAGE)检测了两种类型的胃癌组织的整体基因表达谱，并与数据库中其他正常组织和肿瘤组织的120多个SAGE文库进行了比较。我们已经鉴定出至少8个在低分化型胃癌中高表达的基因/标签。其中，再生基因IV(Reg IV)在胃癌中高表达，而在食道癌、肺癌、乳腺癌和肝癌中不表达。原位杂交证实在胃癌细胞中有较强的表达。将Reg IV基因导入胃癌细胞系，结果表明，Reg IV蛋白能分泌到培养上清液中，并刺激细胞生长。我们还分析了同一患者的原发胃癌及其转移瘤的基因表达谱。已鉴定出3个基因/标签(γ、COP、p21和未知标签)在转移瘤中表达显著降低或缺失。COP是形成γ包衣复合体的7个亚基之一，调节高尔基体和内质网之间的转运。激光捕获显微切割富集靶细胞后，RTPCR法证实转移瘤中γCOP的表达明显降低。我们正在研究这些基因在食道和胃的癌前病变中的表达。本研究中检测到的未知标签可能是胃癌发生的候选新基因。我们确定了几个在散发性(硬化型)胃癌中特异表达的标签，称为SESS。反向SAGE和5‘RACE方法将克隆可能参与食道癌发生发展的新基因，并作为治疗靶点。

To understand the detailed molecular mechanism of development and progression of esophageal and gastric cancer, we examined global gene expression profile in two types of primary gastric cancer through serial analysis of gene expression (SAGE), and compared with over 120 SAGE libraries of other normal and tumor tissues in the database. We have identified at least 8 genes/tags highly expressed in poorly differentiated type gastric cancer. Among them, regenerating gene type IV (Reg IV) was highly expressed in gastric cancer but not in cancer of the esophagus, lung, breast, and liver by RT-PCR. Strong expression was confirmed in gastric cancer cells by in situ hybridization. Introduction of Reg IV gene into gastric cancer cell line revealed that Reg IV protein was secreted into culture media and stimulated cell growth. We have also analyzed the gene expression profiles of the primary gastric cancer and its metastatic tumor from the same patient. It was identified 3 genes/tags (γCOP, p21 and unknown tag) whose expression was markedly reduced or lost in metastatic tumor. γCOP is one of the seven subunits forming COPI coat complex and mediates transport between Golgi and the endoplasmic reticulum. After laser capture microdissection to enrich target cells, obvious reduction in γCOP expression was confirmed in metastatic tumors by RT-PCR. We are studying the expression of these genes in precancerous lesions of the esophagus and stomach. Unknown tags detected in this study must be candidate novel genes for stomach carcinogenesis. We identified several tags specifically expressed in scattered (scirrhous) type gastric cancer, called SESs. Reverse SAGE and 5'RACE method will clone novel genes which may participate in development and progression of esophago-gastric cancer and serve as therapeutic targets.